Apparatus for measuring concentration of specific constituent

ABSTRACT

The present invention provides a measuring method most suitable for measuring the concentrations of specific constituents, especially urine protein level and sugar level. After a protein-contained liquid sample is opacified by heating or while the sample is being heated, a light is projected to the liquid sample. The concentration of protein is determined from the intensity of light transmitted through the sample or scattered from the sample. In a urinalysis, an angle of rotation of the sample is measured before the sample is opacified, and in addition, intensity of the transmitted light or scattered light of the opacified urine is measured, whereby the urine sugar and protein levels are obtained.

BACKGROUND OF THE INVENTION

The present invention relates to a method of measuring a concentrationof a specific constituent in a liquid sample, more particularly a methodof measuring a protein level (albumin concentration) and a sugar level(glucose concentration) of urine collected from humans or animals, andan apparatus for measuring them. The urine sugar level and urine proteinlevel reflect the health conditions. So, an easy-to-use and accuratemeasuring method has been sought.

Hitherto, a urine test has been conducted by dipping a test paperimpregnated with a reagent by a testing constituent such as sugar andprotein into urine, and examining a color reaction of the test paper bya spectrophotometer. This test method requires different kinds of testpapers for different testing constituents, and a new test paper isrequired for each test, thereby leading to a high running cost. Therealso has a limit to automatizing the process for labor saving.

When the urine test is done by this method at home, a layman shouldmount and replace test papers. It is not so pleasant a job and has beena block to the spread of the urine testing unit among the households.

Then, a urine test requiring no such expendable supplies as a test paperis proposed in an international patent application with a giveninternational publication No. WO97/18470. The idea of this applicationis that the urine sugar and urine protein levels are quantified bymeasuring the angle of rotation of the urine since glucose and albuminare optically active, while other urine constituents show little opticalrotatory power.

When a light is propagated through a liquid containing an opticallyactive substance, the direction of polarization rotates in proportion tothe concentration of the optically active substance. It is expressed inthe following equation.

    A=L×α                                          (1)

where:

L: measuring optical path length

A: angle of rotation [degree]

α: specific angle of rotation of optically rotatory substance

If, for example, a light with a wavelength of 589 nm is propagated 100mm through a glucose aqueous solution of 100 mg/dl in concentration, thedirection of polarization of the light rotates 50×10⁻³ degrees.

Utilizing such property, the sugar and protein levels in urine arecalculated by using the above equation. Shown in Table 1 are thespecific angles of rotations of aqueous solutions of glucose and albuminat 20° C.

                  TABLE 1                                                         ______________________________________                                        Wavelength     589 nm    670 nm                                               Glucose                       40 degrees                                      Albumin              -60 degrees                                                                          -43 degrees                                       ______________________________________                                    

In a case N kinds of optically active substances are contained in asolution, the angle of rotation of the solution is given as follows:

    A=L×(α.sub.1 ×C.sub.1 +α.sub.2 ×C.sub.2 + . . . +α.sub.N ×C.sub.N)                          (2)

where:

L: measuring optical path length

A: angle of rotation [degrees]

α_(n) (n=1, 2, . . . , N): specific angle of rotation of substance n (N:natural number)

C_(n) : concentration of substance n [kg/1]

αn: specific angle of rotation of substance n

As is evident from equation (2), the measured angle of rotation of thesolution has an information about the concentrations of the pluraloptically active substances dissolved in the solution. That is, theangles of rotation measured of urine is a sum of the angle of rotationcaused by glucose and that caused by albumin. Since the specific angleof rotation differs with the wavelength of propagated light, the anglesof rotation are measured with different wavelengths of light in thismethod. And the sugar and protein levels in urine are calculated bysimultaneous equations of equation (2).

In this method, with one wavelength of a light source, either the sugaror protein level in urine can be calculated if the concentration of theother is known. But if neither the sugar or protein level in urine isknown, two or more light sources are required. Another shortcoming isthat because there is not much difference between the change in specificangle of rotation of glucose which occurs with the change in lightwavelength and that of albumin as shown in Table 1, no accuratedetermination of the sugar and protein levels in urine can be hoped foreven if a plurality of light sources are used. Especially because theprotein level in urine is smaller in one order of the magnitude than thesugar level, the accuracy in determination is low.

BRIEF SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a methodof determining a concentration of a specific constituent in a liquidsample, especially a protein concentration with high accuracy, which issuitable for urinalysis, eliminating the problems mentioned above.

According to the present invention, a liquid sample containing proteinis opacified by heating, and a light is then projected on the sample andthe intensity of the light which passed through or scattered in thesample is measured. In this way, the concentration of protein in thesample can be determined accurately. This method is most suitable forurine test.

The healthy adult usually discharges 1,000 to 1,500 ml of urine a day.Of that amount, the total solid contents come to 50 to 70 g. Of thesolid contents, about 25 g are inorganic substances which consist mainlyof sodium chloride, potassium chloride and phosphoric acid. Most of themare dissolved and ionized in urine. The rest are organic substances,mainly urea and uric acid, but sugar or glucose and protein are alsopresent through small in quantity. The protein in urine is essentiallyalbumin. Glucose is discharged into urine usually in 0.13 to 0.5 g aday. From this and the amount of urine, the glucose level in urine orthe urine sugar level is estimated at not larger than 50 mg/dl on theaverage. However, with diabetics, the figure is several hundred mg/dland can be as high as several thousand mg/dl. In other words, the valuesfor diabetics can be 10 to 100 times as high as the normal level. On theother hand, albumin is usually still less than glucose and dischargedinto the urine in 3 to 60 mg a day. Calculated from that and the amountof urine, the albumin concentration in urine or the urine protein levelis estimated normally at not larger than 6 mg/dl. But the urine proteinlevel in patients with kidney disorder can reach 100 mg or more/dl--10times as high as the normal level.

Such abnormal protein levels in urine can be detected on the basis ofthe intensity of the transmitted or scattered light. Furthermore,measurement of the angle of rotation of urine provides information onoptically active substances, that is, glucose and albumin. If,therefore, the angle of rotation of urine is determined in advance andthe urine is then heated thereby being opacified, the urine sugar levelcan be determined with high accuracy by measuring the degree of thewhite turbidity. Urine samples which are difficult to be opacified byheating are mixed with a bivalent metal ion or acid before heating so asto facilitate whitening.

Thus realized is a urine test method ease to maintain and control,requiring no expendable supplies.

In the present invention, the intensity of the transmitted or scatteredlight is measured on a heat-treated protein containing liquid sample.Determination can be made in another way in which a light is projectedon the liquid sample being heated, and the intensity of the transmittedor scattered light is measured thereby determining the proteinconcentration from the change with the temperature of the liquid samplein those light intensities.

In still another method according to the present invention, while thesample is heated, the intensity of the transmitted or scattered light ismeasured at two different temperatures. The protein concentration can becalculated on the basis of intensity ratio in the two measurements ofthe transmitted or scattered light.

While the novel features of the invention are set forth particularly inthe appended claims, the invention, both as to organization and content,will be better understood and appreciated, along with other objects andfeatures thereof, from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic diagram showing the configuration of a measurementapparatus in an embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating the output voltage inrelation to the albumin concentration of the aqueous solution inmeasurements using the measurement apparatus.

FIG. 3 is a schematic diagram showing the configuration of a measurementapparatus in another embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the relation of thetemperature and output voltage of the photosensor to the albuminconcentration of the aqueous albumin solution in measurements using themeasurement apparatus

FIG. 5 is a characteristic diagram illustrating the relation between thealbumin concentration of the solution known from the precedingmeasurement and R (ratio of the intensity of the transmitted light at70° C. to that at 75° C.).

FIG. 6 is a schematic diagram showing the configuration of a measurementapparatus in a still further embodiment of the present invention.

FIG. 7 is a characteristic diagram showing the relation between thealbumin concentration in the aqueous solution known from a measurementusing the same apparatus and R (ratio of the intensity of thetransmitted light at 70° C. to that at 75° C.).

FIG. 8 is a schematic diagram showing the configuration of a measurementapparatus in still another embodiment of the present invention.

FIG. 9 is a schematic diagram showing the configuration of a measurementapparatus in yet another embodiment of the present invention.

FIG. 10 is a characteristic diagram showing the output voltage inrelation to the albumin concentration of the aqueous solution in thesame measurement apparatus.

FIG. 11 is a schematic diagram showing the configuration of an apparatusin a still further embodiment of the present invention.

FIG. 12 is a characteristic diagram showing the relation between thealbumin concentration of the aqueous solution known from the samemeasurement and r (ratio of the intensity of the scattered light at 70°C. to that at 75° C.).

FIG. 13 is a schematic diagram showing the configuration of ameasurement apparatus in a still another embodiment of the presentinvention.

FIG. 14 is a characteristic diagram showing the relation between theconcentration of albumin in urine mixed with potassium chloride and theoutput voltage of the photosensor known from yet another embodiment ofthe present invention.

FIG. 15 is a characteristic diagram showing the relation between theconcentration of albumin in urine mixed with magnesium chloride and theoutput voltage of the photosensor known from the same embodiment of thepresent invention.

FIG. 16 is a characteristic diagram showing the relation between theconcentration of albumin in urine mixed with acetic acid and the outputvoltage of the photosensor known from a still further embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The method of measuring the concentration of specific constituentaccording to the present invention comprises the steps of: heating aliquid sample containing protein to obtain an opacified sample;projecting a light on the opacified sample; detecting the lighttransmitted through the opacified sample or scattered from the opacifiedsample out of the projected light; and determining a concentration ofprotein in the liquid sample on the basis of the intensity of thedetected light.

The measuring method according to the present invention is especiallyuseful for urinalysis.

Urine is opacified and whitened when heated up to 60 to 80° C. That isbecause albumin, a protein contained in urine, coagulates into a macrocolloid. The other constituents than albumin are all so small inmolecular weight that the scattering of light on them can be ignored. Itis also noted that heating up to that temperature will not affect theother constituents including glucose. On this ground, the intensity ofthe light transmitted through urine or scattered from urine out of thelight projected on the urine depends on the urine protein level. Withinthe albumin concentration range where the urine protein level ismeasurable, it is considered that the intensity of the transmitted lightis roughly proportional to the urine protein level. That is to say, itis possible to determine the albumin concentration in urine or urineprotein level by projecting a light on opacified urine, measuring theintensity of the scattered or transmitted light and comparing it againsta prepared analytical line (a relational expression between the albuminconcentration of the aqueous solution and the scattered or transmittedlight intensity).

In urinalysis, substantially parallel light rays with a wavelength ofnot shorter than 500 nm are projected on a urine sample. The specificangle of rotation of an optically active substance increases with thedecrease of wavelength as shown in Table 1 until abnormal scattering byoptically rotatory dispersion appears. This means that the shorter thewavelength of light rays, the higher the determination accuracy. Withlight rays with a wavelength of not longer than 500 nm, however, theabsorbance by urine constituents like urochrome increases, making thedetermination less accurate on the contrary.

By measuring an angle of rotation of urine before heating, it becomespossible to determine a urine sugar level with high accuracy as well asthe urine protein level. First, an intensity of the transmitted light orscattered light is checked against analytical line thereby calculatingthe urine protein level. Substituting the urine protein level androtation angle obtained into equation (2) gives the urine sugar level.

In a preferred mode of the present invention, a light is projected onthe protein-containing sample being heated, and measurement is taken ofthe intensity of the light transmitted through the sample or scatteredfrom the sample out of the light projected on the sample. The whiteturbidity of the sample increases with the rise of temperature. So, ifthe sample is heated and the transmitted light or scattered light isdetected simultaneously, the concentration of protein in the sample canbe determined from those changes with temperature. It is not necessaryto measure the intensity of the transmitted light or scattered lightcontinuously. Instead, determination can be made by measuring theintensity of the transmitted light or scattered light at only two pointsbetween 60 and 80° C., and using the ratio of these intensities. Forexample, the concentration of protein can be calculated from the ratioof the intensities of transmitted light at 75° C. to that at 70° C.According to this method, the influence of the transmittance of thesample before heating can be eliminated. That also can remove theinfluence of scattering and the like by substances other than protein.

Liquid samples containing proteins like urine are opacified when heatedto 60 to 80° C. However, some samples with some compositions do notopacified by heating even containing an enough amount of protein. It isdifficult to opacify urine with an unusually high pH value, for example.By adding bivalent metal ions like calcium ions and magnesium ions tosuch sample, it is possible to facilitate the coagulation of proteincontained therein. They are added in the form of chloride, for example.In the case calcium ions are used, the amount of calcium ions to add ispreferably not lower than 0.2 m mol (millimole) per 1 dl of the sample.In the case of magnesium ion, the amount of magnesium ions to add ispreferably not lower than 0.1 m mol per 1 dl of the sample. In place ofsuch bivalent metal ions, an acid can be added to the sample to lowerthe pH of the sample, preferably to 5.5 or below. This way, thecoagulation of protein can similarly be promoted. The acid to add ispreferably acetic acid or phosphoric acid.

The apparatus for measuring a concentration of a specific constituent ofthe present invention comprises: a sample cell to hold a liquid samplecontaining protein; a heater for heating the liquid sample in the samplecell; a temperature measurement unit for measuring the temperature ofthe liquid sample; a light source for projecting substantially parallelmonochromatic light lays on the liquid sample; and a photosensor fordetecting the light transmitted through the liquid sample out of theprojected light and outputting a signal corresponding to the intensityof the light detected.

In a preferred mode of the present invention, the apparatus formeasuring a concentration of a specific constituent further comprises amodulator for modulating the substantially parallel light rays projectedfrom the light source and a lock-in amplifier for the phase-sensitivedetection of a signal outputted from the photosensor referring to thesignal modulated by the light modulation unit.

In another preferred mode of the present invention, the apparatus formeasuring a concentration of a specific constituent comprises: amagnetic field application unit for applying a magnetic field on theliquid sample; a magnetic field sweep unit for sweeping the magneticfield; a magnetic field sweep unit for vibration-modulation of themagnetic field; a polarizer, mounted between the monochromatic lightsource and the sample cell, for transmitting a specific polarized lightcomponent only out of the substantially parallel light rays projectedfrom the light source; an analyzer, provided before the photosensor, fortransmitting a specific polarized light component only out of thesubstantially parallel light rays passed through the sample cell; alock-in amplifier for the phase-sensitive detection of output signalsfrom the photosensor referring to the signal modulated by the magneticfield modulation unit; and a calculator for calculating the angle ofrotation of the liquid sample and intensity of the transmitted light onthe basis of the output signal from the lock-in amplifier.

In still another preferred mode of the invention, the apparatus formeasuring the concentration of specific constituent further comprises: amagnetic field application unit for applying a magnetic field on theliquid sample; a magnetic field sweep unit for sweeping the magneticfield; a magnetic field modulation unit for vibration-modulation of themagnetic field, a polarizer, mounted between the light source and thesample cell, for transmitting a specific polarized light component onlyout of the light rays projected from the light source; an analyzer fortransmitting a specific polarized light component only out of the lightrays passed through the sample cell; a photosensor for detecting thelight transmitted through the analyzer and outputting a signalcorresponding to the intensity of the detected light; a beam sampler totake out part of the light rays transmitted through the sample cell; aphotodetection unit for detection of the light taken out by the beamsampler and for outputting a signal corresponding to the intensity ofthe detected light; a lock-in amplifier for the phase-sensitivedefection of output signals from the photosensor referring to the signalmodulated by the magnetic field modulation unit and receiving the outputsignal from the photodetection area at the same time; and a calculatorfor calculating the angle of rotation of the liquid sample and intensityof the transmitted light according to the output signal from the lock-inamplifier.

Another apparatus for measuring a concentration of a specificconstituent of the present invention comprises: a sample cell to hold aliquid sample containing protein; a heater for heating the liquid samplein the sample cell; a temperature measurement unit for measuring thetemperature of the test sample; a light source for projectingsubstantially parallel monochromatic light rays on the liquid sample;and a photosensor for detecting the light scattered from the liquidsample out of the projected light rays and outputting signalscorresponding to the intensity of the light detected.

In a preferred mode of the present invention, the apparatus formeasuring a concentration of a specific constituents comprises: amodulation unit for modulating the substantially parallel light rays; amagnetic field application unit for applying a magnetic field on thetest sample; a unit for sweeping the magnetic field; a magnetic fieldmodulation unit for vibration-modulation of the magnetic field; apolarizer, mounted between the light source and the sample cell, fortransmitting a specific polarized light component only out of the lightrays projected from the light source; an analyzer for transmitting aspecific polarized light component only out of the light raystransmitted through the sample cell; a photosensor for detecting thelight transmitted through the analyzer and for outputting signalscorresponding to the intensity of the light detected; a photodetectionunit for outputting signals corresponding to the intensity of the lightdetected; a lock-in amplifier for reception of signals from thephotodetection unit and for the phase-sensitive defection of outputsignals from the photosensor referring to the signal modulated by themagnetic field modulation unit; and a calculator for calculating anangle of rotation of the liquid sample and the intensity of thetransmitted light according to the output signal from the lock-inamplifier.

The present invention can utilized in determination of proteinconcentration in a solution. In addition, according to the presentinvention, it is also possible to determine concentrations of opticallyrotary substances further being contained in the solution. Hereafter,methods of determining the sugar and protein levels in urine aredescribed in detail with reference to the accompanying drawings inembodiments of the present invention.

EXAMPLE 1

FIG. 1 shows a configuration of a measurement apparatus used in thepresent embodiment. An irradiation module 1 has an optical system withthe semiconductor laser as a light source and a semiconductor laserdriving circuit. This irradiation module 1 projects a substantiallyparallel light with a wavelength of 670 nm and an intensity of 5 mW on asample cell 2. The sample cell 2 is cylindrical with the two ends 10 mmin diameter made of glass as transmitting surfaces and has a substantiallight path length of 50 mm. A photosensor 3 detects the light projectedfrom the irradiation module 1 and transmitted through the sample cell 2.A lock-in amplifier 4 makes phase-sensitive detection of the outputsignal of the photosensor 3 referring to a modulated signal emitted tothe irradiation module 1 from a signal generator 5 and outputs a signalcorresponding to the intensity of the transmitted light. Here, thesignal generator 5 supplies a modulation signal to the irradiationmodule 1 so as to pulse-modulate the light to be projected from theirradiation module 1 in synchronization with that signal.

The light transmitted through a heat-treated urine sample was determinedusing this apparatus. This determination was performed in the followingway. First, albumin solutions with a concentration of 100, 300 or 1,000mg/dl were prepared with urine as a solvent of which the albuminconcentration had been found to be not higher than 10 mg/dl by using atest paper. These albumin solutions and the urine used as the solventwere heated for 5 minutes at 75° C. and cooled down to 35° C. They werethen poured into the respective sample cells 2 and the intensity of thetransmitted lights were measured.

The results or the output signals (voltage) from the lock-in amplifier 4are plotted in FIG. 2. There, the output voltage is indicatedlogarithmically on the axis of ordinates and the concentration of thealbumin solution on the axis of abscissas. The concentration of Orepresents the urine. As indicated, a relation between the outputvoltage and the albumin concentration is approximated to a straightline. By using this straight line as an analytical line, therefore, itis possible to determine the concentration of albumin or protein levelin an unknown urine sample.

Using this apparatus, a urine sample was analyzed which had been foundto have an albumin concentration of not lower than 100 mg/dl and nothigher than 250 mg/dl by using a test paper. It showed that the outputvoltage of the lock-in amplifier 4 was 0.87 V. The concentration ofalbumin as found from the analytical line in FIG. 2 was 120 mg/dl,agreeing with the results obtained by using a test paper.

Similarly, another urine sample was analyzed which had been found tohave an albumin concentration of not lower than 300 mg/dl and not higherthan 500 mg/dl by using the test paper. The result was that the outputvoltage of the lock-in amplifier 4 was 0.63 V. The albumin concentrationfound from the analytical line shown in FIG. 2 was 400 mg/dl. It is inagreement with the results obtained by using the test paper.

As shown in the present embodiment, protein level of urine can bedetermined with high accuracy by heating the urine and measuring theintensity of the transmitted light after heating the urine. Besides, noexpendable supplies like test papers are required. Therefore, thismethod is high in practicality.

EXAMPLE 2

The configuration of the measurement apparatus used in the presentembodiment is shown in FIG. 3. In this embodiment, while heating aprotein-containing liquid sample such as urine and detecting atemperature thereof, an intensity of a light transmitted through theliquid sample is measured. As in Example 1, a light is projected to asample cell 12 from an irradiation module 11. The sample is poured intothe sample cell 12. A photosensor 13 detects the light projected fromthe irradiation module 11 and transmitted through the sample cell 12.Then, a signal generator 15 supplies a modulation signal to theirradiation module 11 thereby pulse-modulating the light to be projectedin synchronization with this signal. A lock-in amplifier 14 makesphase-sensitive detection of the output signal of a photosensor 13referring to the modulation signal emitted to the irradiation module 11from the signal generator 15. This output voltage of the lock-inamplifier 14 corresponds to the intensity of the transmitted light.Around the sample cell 12 is provided a solenoid coil-shaped heater 18to heat the liquid sample in the sample cell 12. The heater 18 is formedwith 500 turns of an enameled wire. A coiled heater driver 19 suppliesthe heater 18 with a current of up to 5 A according to the command froma computer 17. A thermocouple 10, mounted close to the sample cell 12,practically detects the temperature of the liquid sample in the samplecell 12. A temperature indicator 16 indicates the temperature of theliquid sample detected by the thermocouple 10 and sends the value to thecomputer 17. The output or intensity of the transmitted light detectedby the lock-in amplifier 14 is also supplied to the computer 17. Then,the computer 17 send the heater driver 19 the command to heat the liquidsample according to the preset program. The computer 17 also measuresthe temperature of the liquid sample and the intensity of thetransmitted light.

The procedure of urinalysis in the present embodiment is hereinafterdescribed. Albumin solutions with a concentration of 100, 300 or 1,000mg/dl were prepared using urine as a solvent of which an albuminconcentration had been found to be not higher than 10 mg/dl by using atest paper. These albumin solutions and the urine used as the solventwere poured into the respective sample cells 12 and heated from 35° C.to 80° C. at a rate of 2° C./min. While heating the samples, theintensity of the transmitted light was determined every 6 seconds. Theresults are plotted in FIG. 4, with the axis of abscissas representingthe temperature of the sample and the axis of ordinates the lock-inamplifier output voltage for each concentration of sample whichcorresponds to the intensity of the transmitted light. Also plotted inFIG. 5 is the ratio R which indicates a ratio of the intensity of lighttransmitted through the liquid sample at 75° C. to that at 70° C. asdefined below.

R=(intensity of transmitted light at 75° C.)/(intensity of transmittedlight at 70° C.)

R is indicated logarithmically on the axis of ordinates. As is apparentfrom FIG. 5, a relation between R and the albumin concentration of theliquid sample is approximated to a straight line. By using this straightline as an analytical line, therefore, determination can be made of theconcentration of albumin or protein level in an unknown urine sample.The method of the present embodiment allows more accurate determinationthan that in Example 1, because it is possible to except impedimentalfactors such as a transmittance of the liquid sample before heating.

Using this apparatus, urine was tested that had been found to not lowerthan 100 mg/dl and not higher than 250 mg/dl in albumin concentration byusing a test paper. R was 0.89. The albumin concentration of the urinewas found to be 120 mg/dl from the R and the analytical line in FIG. 5.This value agrees with the results obtained by using the test paper.

Similarly, determination was also made of another urine which had beenfound to be not lower than 300 mg/dl and not higher than 500 mg/dl inalbumin concentration by using a test paper. The result was that R was0.67. From the R and the analytical line in FIG. 5, the albuminconcentration of the urine was found to be 400 mg/dl, agreeing with theresults obtained by using the test paper.

As shown, the method in the present embodiment allows accuratedetermination of protein concentration of the urine. Besides, noexpendable supplies such as a test paper are required.

EXAMPLE 3

The configuration of a measurement apparatus used in the presentembodiment is shown in FIG. 6. In the present embodiment, an angle ofrotation of a liquid sample was determined first at normal temperature.The sample was then heated. While heating, measurement was taken of thetemperature of the sample and the intensity of a light transmittedthrough the sample.

The basic principle of measuring the angle of rotation by the presentapparatus is the optical zero-order method based on the vibration of theplane of polarization using the Faraday effect. An irradiation module 21is the same as the one used in Example 1 and projects substantiallyparallel light rays with a wavelength of 670 nm and an intensity of 5mW. An polarizer 33 transmits only the component of a specific directionout of the projected light rays. A sample cell 22 is the same as the oneused in Example 1. The liquid sample placed in it modulates thedirection of polarization of the transmitting light rays by a very smallwidth due to the optical Faraday effect. An analyzer 34 is arranged inthe orthogonal Nicol state in relation to a polarizer 33 at first, androtates with the transmission axis of the polarizer 33 as an axis ofrotation. If the polarizer 33 and the analyzer 34 are ideal ones, thatis, the extinction ratio is infinite, then the transmitted light doesnot reach a photosensor 23. In practice, however, the extinction ratioof a polarizer and an analyzer can not be infinite. The extinction ratioof the polarizer 33 and the analyzer 34 used in the present embodimentis approximately 5,000, and therefore some 1 μW of the transmitted lightarrives at the photosensor 23. This intensity of light is enough fordetermination of the intensity of the transmitted light.

A lock-in amplifier 24 makes phase-sensitive detection of an outputsignal of a photosensor 23, referring to a modulated signal emitted tothe irradiation module 21 from a signal generator 25.

When the angle of rotation is determined, a switch 35 is connected tothe terminal A to supply to a coil-shaped heater driver 29 the signal ofthe signal generator 25 as a magnetic field modulation signal. Whenmeasuring the transmitted light, the switch 35 is connected to theterminal B to send the signal to the irradiation module 21 as amodulation signal of the projected light.

The heater driver 29 supplies a heater 28 with a current of up to 5 A inaccordance with a command from a computer 27. In determining the angleof rotation, however, the heater 28 and heater driver 29 apply amagnetic field on the liquid sample in the sample cell 22 in accordancewith a command from the computer 27. They can also sweep this magneticfield while modulating it. In other words, the heater 28 in the presentapparatus can apply a magnetic field on the liquid sample whendetermining the angle of rotation and performs its original function asa heater when the liquid sample is heated. A thermocouple 20, mountedclose to the sample cell 22, practically detects the temperature of thesample in the sample cell 22. A temperature indicator 26 indicates atemperature of the sample detected by the thermocouple 20 and sends thevalue to the computer 27 at the same time.

In that setup, the angle of rotation is first determined in accordancewith the command from the computer 27, and then determination is made ofthe temperature of the sample and the intensity of the light transmittedthrough the sample while heating the sample. By this, it is possible todetermine the sugar and protein levels in the sample by one measurement.

The procedure of testing urine using the present apparatus ishereinafter explained.

First, albumin solutions with a concentration of 100, 300 and 1,000mg/dl were prepared with urine as a solvent of which the albuminconcentration had been found to be not higher than 10 mg/dl by using atest paper. These albumin solutions and the urine used as the solventwere placed in the respective sample cells 22 and heated from 35° C. to80° C. With a heating velocity set at 2° C., the intensity of thetransmitted light was determined every 6 seconds.

The ratio R that is a ratio of the intensity of the light transmittedthrough the solution at 75° C. to that at 70° C. was calculated in thesame way as in Example 2. The ratio R was plotted in relation to therespective concentrations in FIG. 7, with the axis representing Rlogarithmically.

With the curve in FIG. 7 as an analytical line, the albuminconcentration in the urine or the urine protein level can be determined.It is noted that the degree of polarization of a linearly polarizedlight propagating through the urine decreases with the rise ofturbidity. That is, polarization is canceled by scattering. Because ofthis cancellation of polarization, therefore, the analytical line inFIG. 7 is not a straight line unlike that obtained in Example 2 andshown in FIG. 5.

Using the present apparatus, determination was then made the same way asabove of a urine sample of which the glucose concentration had beenfound to be not higher than 50 mg/dl, and the albumin concentration notlower than 100 mg/dl and not larger than 250 mg/dl by using test papers.

First, the angle of rotation was determined. The result was:

    A=-19.8×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the transmitted light. From this was obtained:

    R=0.85

From this ratio R and the analytical line in FIG. 7, the albuminconcentration was determined to be 120 mg/dl. By solving equation (2)with that albumin concentration and A, the glucose concentration wasfound to be 30 mg/dl. These are in agreement with the results obtainedby using the test papers.

Using the present apparatus, another urine sample was also tested ofwhich the glucose concentration had been found to be not lower than 100mg/dl and not higher than 250 mg/dl, and the albumin concentration notlower than 300 mg/dl and not larger than 500 mg/dl by using test papers.

First, the angle of rotation was determined. The result was:

    A=-56×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the transmitted light. From the result was obtained:

    R=0.62

From this ratio R and the analytical line in FIG. 7, the albuminconcentration was determined to be 400 mg/dl. By solving equation (2)with the albumin concentration and A, the glucose concentration wasfound to be 150 mg/dl. These are in agreement with the results obtainedby using the test papers.

According to the present embodiment as shown, the urine protein leveland urine sugar level can be determined by one measurement if the angleof rotation of the urine is first measured, and the sample is thenopacified by heating and its white turbidity is measured. This way, theurine protein level and urine sugar level can be measured without usingexpendable supplies such as a test paper. Thus this method is high inpracticality.

EXAMPLE 4

The method in the present embodiment is hereinafter explained in detailwith reference to FIG. 8.

In the present embodiment, too, an angle of rotation of urine is firstmeasured. Then the intensity of light transmitted through the urine ismeasured while heating the urine and measuring the temperature of theurine.

The basic principle of measuring the angle of rotation of the presentapparatus is the same as that in Example 3.

As in Example 1, a polarizer 53 transmits only the component of aspecific direction out of substantially parallel light rays projected byan irradiation module 41. A sample cell 42 is the same as the one usedin Example 1. A liquid sample,placed in it modulates the direction ofpolarization of the transmitting light by a very small width due to theoptical Faraday effect. A polarizer 53 and an analyzer 54 are arrangedin the orthogonal Nicol state. When the angle of rotation is determined,a switch 55 is connected to the terminal A to supply to a coil-shapedheater driver 49 a signal of a signal generator 45 as a magnetic fieldmodulation signal. When measuring the transmitted light, the switch 55is connected to the terminal B to send a signal to the irradiationmodule 41 as a modulation signal of the light to be projected. A beamsampler 58 takes out part of the light transmitted through the liquidsample. A photosensor 56 detects the light taken out and emits a signalaccording to the intensity of the light. The switch 57, synchronizedwith the switch 55, is so changed over that an output signal of aphotosensor 43 is supplied to a lock-in amplifier 44 when measuring theangle of rotation and the output signal of the photosensor 56 issupplied to a lock-in amplifier 44 when measuring the transmitted light.In measuring the angle of rotation, a heater 48 and the heater driver49, as in Example 3, apply a magnetic field on the liquid sample inaccordance with a command from a computer 47. They can also sweep themagnetic field while modulating it. A thermocouple 40, mounted close tothe sample cell 42, practically detects the temperature of the liquidsample in the sample cell 42. A temperature indicator 46 indicates thetemperature of the liquid sample detected by the thermocouple 40 andsends the value to the computer 47 at the same time.

In the present embodiment as in Example 3, the angle of rotation of theliquid sample is first measured, and the intensity of the transmittedlight are determined, while heating the sample and measuring thetemperature of the sample. But the present embodiment is not subject toeffects of the cancellation of polarization unlike Example 3. So, astraight analytical line can be obtained. Actually, the straightanalytical line was obtained in an analysis with the same albuminsolution as in Example 3.

Using the present apparatus, a measurement was conducted on a urinesample of which the glucose concentration had been found to be nothigher than 50 mg/dl, and the albumin concentration not lower than 100mg/dl and not larger than 250 mg/dl by using test papers. First, theangle of rotation was determined. The result was:

    A=-19.8×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the transmitted light. From the result was obtained:

    R=0.89

From this ratio R and the analytical line obtained, the albuminconcentration was determined to be 120 mg/dl. By solving equation (2)with that albumin concentration and A, the glucose concentration wasfound to be 30 mg/dl. These are in agreement with the results obtainedby using the test papers.

Similar measurement was conducted on another urine sample of which theglucose concentration had been found to be not lower than 100 mg/dl andnot higher than 250 mg/dl, and the albumin concentration not lower than300 mg/dl and not larger than 500 mg/dl by using test papers. First, theangle of rotation was determined. The result was:

    A=-56×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the transmitted light. From the result was obtained:

    R=0.67

From this ratio R and the analytical line obtained, the albuminconcentration was determined to be 400 mg/dl. By solving equation (2)with the albumin concentration and A, the glucose concentration wasfound to be 150 mg/dl. These are in agreement with the results obtainedby using the test papers.

According to the present embodiment as shown, the urine protein leveland urine sugar level can be determined by one measurement if the angleof rotation of the urine sample is measured in advance to heat the urinesample and measure the intensity of the light transmitted through thesample whereby determining its white turbidity. In this way, the urineprotein level and urine sugar level can be measured without usingexpendable supplies like a test paper. Thus this method is high inpracticality. Especially in the present embodiment, the conversion fromR to the albumin concentration is easy since a straight analytical linecan be obtained.

In those embodiments, the methods have been explained of finding theurine protein level on the base of the intensity of the lighttransmitted through the urine. In the following embodiments, anexplanation is made about procedures for determining the urine proteinlevel from the intensity of a light scattered from the urine.

EXAMPLE 5

A method based on a measurement of an intensity of a light scatteredfrom a sample is hereinafter explained in detail with reference to FIG.9. As in Example 1, an irradiation module 61 projects light rays to asample cell 62. A liquid sample is placed in the sample cell 62. Thelight rays projected from an irradiation module 61 and scattered whenpassing through the sample in the sample cell 62 is detected by aphotosensor 63, which then outputs a signal. A lock-in amplifier 64makes phase-sensitive detection of an output voltage of the photosensor63 referring to a modulation signal emitted to an irradiation module 61from a signal generator 65 and then outputs a signal corresponding tothe intensity of the scattered light. The signal generator 65 supplies amodulation signal to the irradiation module 61 so as to pulse-insulatethe light to be projected from the irradiation module 61 insynchronization with this signal.

Using this apparatus, a measurement was taken of the intensity of thelight scattered on a urine sample which had been heated and then cooled.Albumin solutions with a concentration of 100, 300 or 1,000 mg/dl wereprepared with urine as a solvent of which the albumin concentration hadbeen found to be not higher than 10 mg/dl by using a test paper. Thesealbumin solutions were heated along with the urine used as the solventfor 5 minutes at 75° C. and cooled down to 35° C. They were then pouredinto the respective sample cells 62, and the intensity of the scatteredlight was determined.

The results or the output voltage from the lock-in amplifier 64 areplotted in FIG. 10. There, the output voltage is indicatedlogarithmically on the axis of ordinates and the concentration ofalbumin solution on the axis of abscissas. The concentration of Orepresents the solvent alone or the urine. As indicated, a relationbetween the output voltage and the albumin concentration is linearlyapproximated to a straight line in the determination of the scatteredlight, too. By using this straight line as an analytical line,therefore, it is possible to determine the concentration of albumin orprotein level in the sample.

Using this apparatus, a urine sample was tested that had been found tonot lower than 100 mg/dl and not higher than 250 mg/dl in albuminconcentration by using a test paper. It showed that the output voltageof the lock-in amplifier 64 was 0.12 V. The concentration of albumin asfound from the analytical line shown in FIG. 10 was 120 mg/dl, agreeingwith the results obtained by using the test paper.

The same way, another urine sample was tested that had been found to notlower than 300 mg/dl and not higher than 500 mg/dl in albuminconcentration by using a test paper. The result was that the outputsignal intensity of the lock-in amplifier 64 was 0.35 V. Theconcentration of albumin as found from the analytical line shown in FIG.10 was 400 mg/dl. It is in agreement with the results obtained by usingthe test paper.

As shown, the urine protein level and urine sugar level can be measuredaccording to the method of the present embodiment. This method alsorequires no expendable supplies like test paper, in addition.

EXAMPLE 6

The configuration of an apparatus used in the present embodiment isshown in FIG. 11. In the present embodiment, while heating a liquidsample and measuring the temperature thereof, the intensity of the lightscattered from the liquid sample is determined. As in Example 1, anirradiation module 71 projects light rays to a sample cell 72. A liquidsample heat-treated at a specific temperature is placed in the samplecell 72. A photosensor 73 detects the light scattered from the liquidsample on propagating through the sample cell 72 after being projectedfrom the irradiation module 71. A lock-in amplifier 74 makesphase-sensitive detection of the output signal of the photosensor 73referring to a modulated signal emitted to the irradiation module 71from a signal generator 75 and then outputs a signal corresponding tothe intensity of the scattered light. There, the signal generator 75supplies a modulation signal to the irradiation module 71 so as topulse-modulate the light rays from the irradiation module 71 insynchronization with this signal. Around the sample cell 72 is arrangedthe same heater 78 as that in Example 3. A coiled heater driver 79supplies the heater 78 with current of up to 5 A according to thecommand from the computer 77. A thermocouple 70, mounted close to thesample cell 72, practically detects the temperature of the liquid samplein the sample cell 72. A temperature indicator 76 indicates thetemperature of the liquid sample detected by the thermocouple 70 andsends the value to the computer 77 at the same time. The output of alock-in amplifier 74 or the intensity of the scattered light is alsosent to the computer 77. The computer 77 then heats the liquid sampleaccording to the preset program and measures the temperature of theliquid sample and the intensity of the scattered light.

The urinalysis method of the present embodiment is hereinafterdescribed. Albumin solutions with a concentration of 100, 300 or 1,000mg/dl were prepared with urine as a solvent of which the albuminconcentration had been found to be not higher than 10 mg/dl by using atest paper. These albumin solutions and the urine used as the solventwere placed in the respective sample cells 72 and heated from 35° C. to80° C. at a rate of 2° C./minute. While heating, the intensity of thescattered light was measured every 6 seconds. Plotted in FIG. 12 is theratio r that is a ratio of the intensity of light scattered at 75° C. tothat at 70° C. with that albumin concentration. The ratio r is definedas follows:

r=(intensity of light scattered at 75° C.)/(intensity of light scatteredat 70° C.)

where r is indicated logarithmically on the axis of ordinates. As iscleared from FIG. 12, a relation between the concentration of albuminand r is approximated by a straight line. By using this straight line asan analytical line, determination can be made of the albuminconcentration or protein level in an unknown urine sample. The method ofurinalysis in the present embodiment allows more accurate determinationthan that in Example 5, because it is possible to except impedimentalfactors such as the transmittance of the sample before heating.

Using this apparatus, a urine sample was tested that had been found tonot lower than 100 mg/dl and not higher than 250 mg/dl in albuminconcentration by using a test paper. The ratio r was found to be 4.6.With this, the albumin concentration was found to be 120 mg/dl from theanalytical line in FIG. 12. It agrees with the results by using the testpaper.

Similarly, another urine sample was tested of which the albuminconcentration had been found to be not lower than 300 mg/dl and nothigher than 500 mg/dl by using test papers. The ratio R was found to be13.3. With this value, the concentration of albumin was found to be 400mg/dl from the analytical line in FIG. 12. It is in agreement with theresults obtained by using the test papers. As shown, the urine proteinlevel can be measured with high accuracy by the present method. Besides,no expendable supplies like test paper are required.

EXAMPLE 7

A method in the present embodiment is hereinafter described in detailwith reference to FIG. 13. In the present embodiment, the angle ofrotation of a liquid sample is first measured. Then, while heating theliquid sample and measuring the temperature of the sample, an intensityof a light scattered from the sample is measured.

A polarizer 93 transmits only the component of a specific direction outof the substantially parallel light rays subjected by an irradiationmodule 81 as same as the one used in Example 1. A sample cell 82 is thesame as the one used in Example 1. A liquid sample placed in itmodulates the direction of polarization of the transmitted light by avery small width. A polarizer 93 and an analyzer 94 are positioned inthe orthogonal Nicol state with the sample cell 82 between them. Aroundthe sample cell 82 is arranged a coil-shaped heater 88. When the angleof rotation is measured, a switch 95 is connected to the terminal A tosupply to a coil-shaped heater driver 89 a signal of a signal generator85 as a magnetic field modulation signal. When measuring the scatteredlight, the switch 95 is connected to the terminal B to send the signalto the irradiation module 81 as an modulation signal of the projectedlight. A photosensor 96 detects the light scattered in passing throughthe liquid sample in the sample cell 82 after being projected from theirradiation module 81. A switch 97 is so changed over that the outputsignal of the photosensor 83 is supplied to a lock-in amplifier 84 whenmeasuring the angle of rotation and the output signal of a photosensor96 is supplied to the lock-in amplifier 84 when measuring the scatteredlight. A thermocouple 80, installed close to the sample cell 82,practically detects the temperature of the liquid sample in the samplecell 82. A temperature indicator 86 indicates the temperature of theliquid sample detected by the thermocouple 80 and sends the value to acomputer 87 at the same time.

That way, as in Example 6, after measuring the angle of rotation of theliquid sample, the temperature of the sample and the intensity of thescattered light is determined while heating the sample.

A urine sample was tested of which the glucose concentration had beenfound to be not higher than 50 mg/dl, and the albumin concentration notlower than 100 mg/dl and not larger than 250 mg/dl by using test papers.

First, the angle of rotation was determined. The result was:

    A=-19.8×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the scattered light, and the following was obtained:

    r=4.6

From this ratio r and the analytical line obtained, the albuminconcentration was determined to be 120 mg/dl. By solving equation (2)with that albumin concentration and A, the glucose concentration wasfound to be 30 mg/dl. These are in agreement with the results obtainedby using the test papers.

Similarly, urinalysis was made of another urine sample which the glucoseconcentration had been found to be not lower than 100 mg/dl and nothigher than 250 mg/dl, and the albumin concentration not lower than 300mg/dl and not larger than 500 mg/dl by test papers.

First, the angle of rotation was determined. The result was:

    A=-56×10.sup.-3 [degrees]

Then, the urine sample was heated and determination was made of theintensity of the scattered light, and the following was obtained:

    r=13.7

From this ratio r and the analytical line obtained, the albuminconcentration was determined to be 400 mg/dl. By solving equation (2)with the albumin concentration and A, the glucose concentration wasfound to be 150 mg/dl. These are in agreement with the results obtainedby using the test papers.

As shown, the method in the present embodiment allows determinations ofurine protein and sugar levels together if the angle of rotation isfirst measured in advance to opacify the urine sample by heating and tomeasure the white turbidity of the urine sample. In this way, it ispossible to find the urine protein level and sugar level without usingexpendable supplies like a test paper.

Noteworthy is that in the present embodiment, only one photosensor isrequired as in the apparatus in the above embodiment.

As shown above in the embodiments, the urine protein level of the samplecan be measured by heating the sample so as to opacify it anddetermining the white turbidity of the sample from the intensity of thetransmitted or scattered light. Also, if the angle of rotation of thesample is measured before heating, the urine protein level and sugarlevel as well can be obtained.

According to the present invention, a urinalysis method can be realizedwhich requires no expendable supplies like test paper, thus providing aurinalysis apparatus easy to maintain and operate.

EXAMPLE 8

According to the preceding embodiments, urine protein and sugar levelscan be determined accurately in most urine samples. However, there aresome samples which are difficult to opacify by heating. Urine sampleswith an abnormally high pH value, for example, will not turn white,because the albumin does not coagulate well. A urine sample ofComparative Example illustrated in FIG. 14 had been found to be in arange of 300-500 mg/dl in protein level by using a test paper and had apH value of 7.0. An intensity of a transmitted light though the urinesample of Comparative Example was observed as same in Example 1 afterheating the urine sample for 5 minutes at 80° C. and cooling down it to35° C. As indicated, white turbidity of the urine sample by heating islow and is far apart from the analytical line in Example 1 which isrepresented by a broken line.

With such urine samples, the addition of bivalent metal irons, i.e.calcium irons and magnesium ions can facilitate the coagulation ofalbumin in the urine sample.

Albumin aqueous solutions were prepared which were 100, 300 and 1,000mg/dl in concentration. Then, those aqueous solutions and pure water asa reference, 1 dl each, were mixed with 22.2 mg of calcium chloride. Theaqueous solutions thus prepared were each heated for 5 minutes at 80° C.and then cooled to 35° C. The heat-treated samples were separatelypoured into a sample cell 2 and the transmitted light was observed.

On the other hand, 22.2 mg of calcium chloride was dissolved in the sameurine sample as in Comparative Example. The Urine sample was heated andthe transmitted light was observed. This shall be Example 8.

Those results are shown in FIG. 14. As is evident from the figure, theaddition of calcium chloride can facilitate the coagulation of albuminin the urine, permitting an accurate determination of the urine proteinlevel.

Then, the effect of the addition of calcium chloride to the urine wasvisually observed. It showed that the white turbidity of the urine rosewith the increase in an additive amount of calcium chloride. But whenthe amount of calcium chloride exceeded 0.2 m mol (millimole)/dl of theurine, the white turbidity did not change any more. From this, itfollows that albumin in the urine can be completely coagulated by adding0.2 m mol or more/dl urine.

But the analytical line also changes with the addition of those bivalentmetal ions unlike when no addition is made. Therefore, it is necessaryto prepare the analytical line of the aqueous albumin solution mixedwith the same amount of calcium chloride as that added to the test urinesample.

A study was made of the addition of magnesium chloride to the same urinesample as above. It was confirmed that the addition of magnesiumchloride in place of calcium chloride facilitates the coagulation ofalbumin in the urine the same way. In this test, when the additiveamount of magnesium chloride exceeded 0.1 m mol/dl urine, the whiteturbidity became unchanged. Magnesium chloride was added to urine in 9.5mg/dl. With this solution, the transmitted light was observed the sameway as above. The results are shown in FIG. 15. From this, it wasconfirmed that accurate measurements were possible with magnesiumchloride, too.

EXAMPLE 9

In the present embodiment, an acid was added to a urine sample which wasdifficult to opacify by heating. It is possible to facilitate thecoagulation of albumin by lowering the pH value of the urine sample withan acid like acetic acid.

A 1% aqueous solution of acetic acid was added to the same urine sampleas in Embodiment 8 in 0.1 ml/dl, thereby opacifying the urine sample.Upon addition of the acidic solution, the pH value of the urine sampledecreased to 5.5. The sample was heated for 5 minutes at 80° C. andcooled down to 35° C. The heat-treated urine sample was placed in thesample cell 1, and measurements were taken of the intensity of thetransmitted light. The measurement was also taken to the urine alone, asa reference.

On the other hand, albumin aqueous solutions were prepared which had aconcentration of 100, 300 or 1,000 mg/dl. Those aqueous solutions andpure water as a reference were mixed with 0.1 ml of the acid/dl,respectively. Thus obtained were each heated for 5 minutes at 80° C. andcooled down to 35° C. Then the similar measurements were taken of theintensity of the transmitted light.

The results are shown in FIG. 16. As shown, the urine protein level canbe determined with high accuracy when the acid is added in place ofbivalent metal ions in Example 8. It was also confirmed that even if thepH value of the urine sample is further lowered by increasing the amountof additive acetic acid, the urine protein can be determined accuratelythe same way.

Although the present invention has been described in terms of thepresently preferred embodiments, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artto which the present invention pertains, after having read the abovedisclosure. Accordingly, it is intended that the appended claims beinterpreted as covering all alterations and modifications as fall withinthe true spirit and scope of the invention.

We claim:
 1. An apparatus for measuring a concentration of a specificconstituent comprising:a sample cell to hold a liquid sample containingprotein; a heater for heating said liquid sample in said sample cell; atemperature measurement unit for measuring the temperature of saidliquid sample; a light source for projecting substantially parallelmonochromatic light rays on said liquid sample; a photosensor fordetecting the light component transmitted through said liquid sample outof the projected light rays and outputting a signal corresponding to theintensity of the detected light rays; a magnetic field application unitfor applying a magnetic field on said liquid sample; a magnetic fieldsweep unit for sweeping said magnetic field; a magnetic field modulationunit for vibration-modulation of said magnetic field; a polarizer,mounted between said light source and said sample cell, for transmittinga specific polarized light component only out of the light raysprojected from said light source; an analyzer, provided before saidphotosensor, for transmitting a specific polarized light component onlyout of the light rays passed through said sample cell; a lock-inamplifier for the phase-sensitive defection of the output signal fromsaid photosensor referring to the modulated signal of said magneticfield modulation unit; and a calculator for calculating an angle ofrotation of said liquid sample and intensity of transmitted light raysaccording to the output signal from said lock-in amplifier.
 2. Theapparatus for measuring a concentration of a specific constituent inaccordance with claim 1,wherein said liquid sample is urine.
 3. Theapparatus for measuring a concentration of a specific constituent inaccordance with claim 2, wherein said light rays projected from saidlight source have a wavelength of not shorter than 500 nm.
 4. Anapparatus for measuring a concentration of a specific constituentcomprising:a sample cell to hold a liquid sample containing protein; aheater for heating said liquid sample in said sample cell; a temperaturemeasurement unit for measuring the temperature of said liquid sample; alight source for projecting substantially parallel monochromatic lightrays on said liquid sample; a photosensor for detecting the lightcomponent transmitted through said liquid sample out of the projectedlight rays and outputting a signal corresponding to the intensity of thedetected light rays; a magnetic field application unit for applying amagnetic field on said liquid sample; a magnetic field sweep unit forsweeping said magnetic field; a magnetic field modulation unit forvibration-modulation of said magnetic field; a polarizer, mountedbetween said light source and said sample cell, for transmitting aspecific polarized light component only out of the light rays projectedfrom said light source; an analyzer for transmitting a specificpolarized light component only out of the light rays passed through saidsample cell; a photosensor for detecting the light rays transmittedthrough said analyzer and outputting a signal corresponding to theintensity of the detected light rays; a beam sampler for taking out partof the light rays transmitted through said sample cell; a photodetectionunit for detecting the light rays taken out by said beam sampler andoutputting the signal corresponding to the intensity of the detectedlight rays; a lock-in amplifier for the phase-sensitive defection ofoutput signals from said photosensor referring to the modulated signalof said magnetic field modulation unit and for receiving the outputsignal from said photodetection unit; and a calculator for calculatingan angle of rotation of said liquid sample and intensity of thetransmitted light according to the output signal from said lock-inamplifier.
 5. The apparatus for measuring a concentration of a specificconstituent in accordance with claim 4, wherein said lock-in amplifierdoes phase-sensitive detection of the output signal of saidphotodetection unit referring to the modulated signal of said magneticfield modulation unit.
 6. An apparatus for measuring a concentration ofa specific constituent comprising:a sample cell to hold a liquid samplecontaining protein; a heater for heating said liquid sample in saidsample cell; a temperature measurement unit for measuring thetemperature of said liquid sample; a light source for projectingsubstantially parallel monochromatic light rays on said liquid sample; aphotosensor for detecting the light rays scattered from said liquidsample out of the projected light rays and outputting a signalcorresponding to the intensity of the detected light; a light modulationunit for modulating the light rays projected from said light source; amagnetic field application unit for applying a magnetic field on saidliquid sample; a magnetic field sweep unit for sweeping said magneticfield; a magnetic unit modulation unit for vibration-modulation of saidmagnetic field; a polarizer, mounted between said light source and saidsample cell, for transmitting a specific polarized light component onlyout of the light rays projected from said light source; an analyzer fortransmitting a specific polarized light component only out of the lightrays passed through said sample cell; a photosensor for detecting thelight rays transmitted through said analyzer and outputting a signalcorresponding to the intensity of the detected light; a photodetectionunit for detecting the light scattered from said liquid sample out ofthe projected light rays and outputting a signal corresponding to theintensity of the detected light; a lock-in amplifier for receiving theoutput signal from said photodetection unit and for the phase sensitivedefection of the output signal from said photosensor referring to themodulated signal of said magnetic field modulation unit; and acalculator for calculating the angle of rotation of said liquid sampleand intensity of the transmitted light according to the output signalfrom said lock-in amplifier.
 7. The apparatus for measuring aconcentration of a specific constituent in accordance with claim 7,wherein said lock-in amplifier does phase-sensitive detection of theoutput signal of said photodetection unit referring to the modulatedsignal of said light modulation unit.
 8. The apparatus for measuring aconcentration of a specific constituent in accordance with claim 6,wherein said liquid sample is urine.
 9. The apparatus for measuring aconcentration of a specific constituent in accordance with claim 8,wherein the light rays projected from said light source have awavelength of not shorter than 500 nm.